Overview
- Climate Central released a global analysis in mid-July that applied a published temperature–sleep model to 1,338 cities and found the average person lost about 56 hours of sleep per year to high nighttime temperatures in 2020–2025, with roughly six hours directly attributable to human-caused warming.
- The study identifies southern India as a major hotspot where people lose between 78 and 91 hours of sleep annually, of which about eight to nine hours are linked to climate change.
- At the city level Chennai records the highest overall night-heat sleep loss (about 93 hours per year) while Bengaluru shows the strongest climate-attributable signal (about eight extra hours per year, roughly 12% of its total heat-related loss).
- Researchers and health experts warn that repeated night heat disrupts the body's cooling needed for restorative sleep and can raise risks of weakened immunity, heart and metabolic disease, poor mental health, lower cognition and reduced workplace safety; older adults, women and low-income households without cooling are most vulnerable.
- The analysis compares observed 2020–2025 nighttime temperatures with a 1970–1975 counterfactual to estimate the climate-attributable share, and authors say the results point to practical responses such as wider access to cooling, heat-aware urban planning and faster emissions cuts to avoid growing sleep and health burdens.